Directive radio system



R. BOWN DIRECTIVE RADIO SYSTEM Nov. 11, 1924. I 1,514,648

Filed Nov. 12 1920 In! 4 V Mung I BY I ATTORNEY,

Patented Nov. 11, 1924.

UNITED STATES PATENT OFFICE.

RALPH BOWN, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

DIRECTIVE RADIO SYSTEM.

Application filed November 12, 1920. Serial No. 428,604.

To all whom it may concern:

Be it known that I, RALPH BOWN, residing at East Orange, in the countyof Essex and State of New Jersey, have invented certain Improvements inDirective Radio Systems, of which the following is a specification.

This invention relates to directive radio systems and especially tomeans for synchronizing the radiation from a plurality of antennaeembraced in an antenna array.

It is well-known that directivity may be obtained in a radio system bygrouping the antenna in a certain predetermined manner and bycontrolling the amplitude and the phase of the oscillations radiated byeach antenna of the group. Such an arrangement is disclosed in thecopending application of George A. Campbell, Serial No. 327,553, filedSeptember 30, 1919.

It is the object of the present invention to provide means for.controlling the frequency of oscillation of each antenna connected withsuch a directive system, so that all of the antennae in an antenna arraywill remain in synchronism automatically, without using high frequencytransmission lines or balancing circuits between the various systems ofsuch an array.

Another object of this invention is to modulate simultaneously and froma central source the oscillations generated by the oscillation circuitsindividual to each antenna of the antenna array. Another object of theinvention is to provide an arrangement for supplying from a centralsource the power necessary to heat the filaments of the vacuum tubesassociated with the oscillation circuits of the antennae.

Other and further objects of this invention will appear from thefollowing description tachbd drawing, which shows one form of embodimentof the invention.

In the arrangement'shown in the figure, a microphone 1, connected inseries with a battery 2 and one of the windings 3 of a repeating coil 4,constitutes a source of the low frequency variations which are impressedupon the other winding 5-of the said repeatin coil, which is connectedwith the grids an filaments of a plurality of vacuum tube modulators M Mand M in parallel.

when read in connection with the at-' The source of low frequencyvariations is represented as a microphone for purpose of illustrationonly, and not to limit the scope of the invention, since any source ofvariation may be employed such as telegraph transmitting devices orother signaling apparatus. Bridged across the plate-filament circuits ofthese modulators in parallel is a source of direct current potential Gwhich is connected 1n series with a choke coil 6 which, if desired, maybe of the iron-core type. This generator and its associated choke coilare likewise bridged across the plate-filament circuit of a plurality ofvacuum tube oscillators, which are associated with a plurality ofantennae constituting. an antenna array. Each antenna circuit comprisesan antenna 7, which is connected to ground through an inductance 8 andcondensers 9 and 10, the said condensers being serially connected witheach other, and together in parallel with the said inductance.

It will be seen that the positive side of the I generator Gr isconnected by conductor 15 and through a retardation coil 11 with theplate of each vacuum tube oscillating device. The negative side of thegenerator G, is connected by conductor 16 and through a retardation coil13 not only to the filament of the vacuum tube oscillator, but alsoto'the midpoint between the two condensers 9 and 10 of the oscillatingcircuit. The grid of the vacuum tube oscillator is connected directlywith the antenna 7 For the. Purpose of heating the filament of eachvacuum tube of each oscillation circuit, current may be supplied from acentral source B to the filaments in parallel over conductors 16 and 17,conductor 16 being common to the plate circuit and the filament heatingcircuit. Although the source offilament-heating current is representedas a battery, it is to be understood that either direct or alternatingcurrent may be used for this purpose, and any appropriate type ofapparatus may be employed. Each 0 the antennae connected with the commonmodulating source has the same type of oscillating circuit, and theseantennae are so spaced geographically as to have an appreciable reactionamong themselves.

Having in mind the foregoing description of the various parts of thisarrangement and the function of each part, this invention will be betterunderstood from the following description of its mode of operation.

When no low frequency variations are impressed upon the modulatingsystem, only the direct current potential set up by the generator G,will be impressed upon the plate-filament circuits of the modulators MM,, M etc., and of the oscillators O O and 0 etc. The impression of adirect current potential across the plate-filament circuit of eachoscillator tube, the filaments of which have been heated, will allow orcause the oscillation circuit of each antenna to function which resultsin the generation and radiation of unmodulated oscillations of adefinite, predetermined frequency depending upon the constants of theoscillation circuit. This action, as is well known, arises from theelectrical instability of circuits of this type. Briefly stated, theimpression of a potential across the plate-filament circuit of anoscillatoreither charges, or varies the charge upon condensers 12 and 9.The effect upon condenser 9, in turn varies the grid potential whichconsequently results in a variation of the plate-filament current. Thecycle of operations, thus begun, will continue o long as a potential isapplied to the platefilament circuit, and the oscillation circuit, ofwhich the antenna forms a part, will continue to generate and radiateoscillations, of predetermined frequency. It is to be noticed that suchgeneration is not dependout upon the impression of low frequencyvariations upon the oscillator.

The oscillation circuits of all the antennae comprised in the array aretuned as closely as possible to the same frequency, and consequentlythere will be generated and radiated oscillations having substantiallythe same frequency. It has been discovered that if two vacuum tubeoscillators are respectively connected to two antenna systems which arein close proximity, it is oftentimes difficult to obtain low frequencybeats between the two oscillators. It has been noticed that when theirfrequencies are brought close to the same value, the oscillations tendto pull into exact synchronism with each other in a manner closelyresembling the action of two alternators connected to the same bus-bars.Furthermore, it has been seen that the frequency of either or bothoscillators, after having been brought to a state of synchronism, willjump discontinu ously from the same value to slightly different valuesas the natural period of oscillation of the respective circuits isaltered, instead of passing smothly from one value to another. Thistendency of adjacent oscillatory circuits to'work into synchronism andto tend to maintain such synchronous condition, is, of course, due tothe coupling effeet which exists between two antenna structuresrelatively adjacent. With a properly designed system the effect is verynoticeably present, even though antenna coupling is so small that onewould anticipate substantially no result therefrom.

In View, therefore, of this inherent characteristic of oscillationcircuits, loosely coupled, the slight variations of frequency of thegenerated oscillations are compensated for, and the resulting radiatedoscillations are in synchronism.

The high frequency oscillations are kept out of the circuits connectedwith the generator Gr and the filament heating source B by means ofreactances-ll, 13 and 14, inserted in the leads connecting theoscillators with the conductors of the said circuits.

When, however, variations are set up in a circuit containing themicrophone 1 by the impression thereon of sound waves, similarvariations will be produced in the gridfilament circuits of themodulators M M and M These variations result in variations of thecurrent flow in the plate-file ment circuits of the same modulators,which causes a difference in potential across the circuit comprising thegenerator G and the choke coil 6, that is to say, across. the points 20and 20. These variationsof potential will result in correspondingvariations in the current flow through the platefilament circuits of theoscillators 0,, O and 0 These variations in current flow will producedifferences in potential across the condensers 12, 9 and 10 which, inturn result in varying the charge upon the gri of the oscillator. Thehigh frequency oscillations which are being generated by eachoscillation circuit are modulated in accordance with the variation ofpotential across the points 20-420 which modulation results from thecurrent variation of the plate-filament circuit of the modulators M Mand M, when low frequency variations are impressed on the saidmodulators. N 0 claim for invention is made for this mode of modulatinghigh frequency oscillations, which is substantially that disclosed inthe copending application of Heising Serial No. 131,868, filed November17, 1916. Furthermore, my invention is not limited to the use of thisparticular system of modulation but may be embodied in arrangements inwhich other and different systems of modulation may be employed.

My invention consists broadly in the application of the observedprinciple of selfsynchronization of oscillation circuits to anarrangement which is designed to obtain directivity in a radio system.The antennae which are associated with the oscillators 0,, O and 0should be so spaced that the effect of any one antenna would always bein synchronism with the effect of any other antenna at the point oflocation of any anple of the wave means of their associated antennae, I

'zation, whereby all the fore referred to, the simplest case of whichis, of course, a linear arrangement where the antennae are spaced apartby an'even multilength. No claim is made by me for the proper s acing ofthe antennae in such an array. y invention lies in the application ofthe principle, heretofore described, to any antenna array, or arrays.

It will be seen that, by. utilizing the principle ofself-synchronization of a plurality of oscillation circuits, loosely.coupled by am further enabled to control the operation and to modulatethe oscillations of the said oscillation circuits from some centralpoint adj acent-to or remote from the place where the said oscillationcircuits are located, andthereb to minimize the cost of installationando maintenance of such systems. The cost of installation is minimized bythe application of the principle of self-synchroniantenna array willremain in synchronism automatically without the use of high frequencytransmission lines or balancing circuits between the various units ofthe array. By means of the arrangement embracing my invention, it isnecessary to have at each antenna unit of such an antenna array only anoscillation circuit connected with a transmission line with which mayalso be connected at some central location a source of modulated directcurrent, for controlling the oscillations radiated from theentire'array. Furthermore, the energy'for filament heating is alsosupplied froma central source over a transmission line to each vacuumtube. Broadly speaking, all apparatus requiring attention except thevacuum tubes associated with the oscillation circuits, is lo-' cated atthe central control point, so that the maintenance costs of such systemis reduced to a minimum.

Although this invention has been described in connection with a specificcircuit arrangement, it is to be understood that it is capable ofembodiment-in other forms and arrangements, without dep-artin from thespirit and scope of the appende claims.

What is claimed is:

1. In a high frequency signaling system, the combination with a luralitof antennae, each having an oscil ation circuit and a multi-electrodethermionic oscillation device associated therewith the antennae beingspaced an even multiple of a wave length apart, of a common modulatingarrangement, whereby the oscillations of each oscillation circuit may besimultaneously varied, and a common source of energy for heating one ofsaid electrodes of the said thermionic devices.

antenna units of an 2. In a high frequenc signaling system, thecombination with a p urality ofantennae, each having an oscillationclrcuit and a multi-electrode thermionic oscillation device associatedtherewith, the antennae being spaced an even multiple of a wave lengthapart, of a common source of energy remote from the said antennae forheating one of the electrodes of the said thermionic device.

3. In a directive radio system in which the antennae are spaced an evenmultiple of a'wave length apart, the method of controlling the wavesradiated from the plurality of antennae having a plurality ofmultielectrode vacuum tube oscillators associated therewith, whichconsists in tuning the oscillation circuits of each antenna tosubstantially the same frequency, impressing upon two of the electrodesof each vacuum tube oscillator waves modulated in accordance with theimpressed signals and allowing the generated oscillations of the variousantennae to interact so as to produce substantial syn- I chronismbetween the various antennae of the current bridged across theplate-filament cir cuits of the saidmodulators and the said oscillators,whereb oscillations may be set up on the said oscillatory circuits inaccordance with the low frequency variations, and means for varying thefrequency of each of the said antennae until the' degree of differencebetween the respective fre uencies is such as to be compensated for by te natural reaction between the respective antennae, whereby absolutesynchronism is obtained.

5. In a high frequency signaling system containing an antenna arrayconsisting of a plurality of antennae spaced at even multiples of a wavelength apart, each of said antennae having individual thereto a vacuumtube oscillation circuit, a power circuit common to all of said vacuumtubes and a modulating circuit common to. all of said antennae andadapted to control the energy output thereof, the method which consistsin tuning the said oscillation circuits to subsubstantially the samefrequency, supplying from a central point to each of said oscillationcircuits the energy to be radiated therefromand simultaneousl modulatingthe energy in each of said osci lation circuits.

6. In a system such as is set forth in claim 1, the method for remotelyoontrollin a directive radio signaling system, whic con sists in settingup from a central point oscillations at each of a plurality of antennaearranged in an antenna array, tuning the said antennae to obtainsubstantial identity of frequency and modulating from a cent tral pointthe oscillations set up at each of said antennae. v

7. In a system such as is set forth in claim 1, the method of remotelycontrolling a directive radio signaling system compris hing a pluralityof thermionic oscillators associated with a plurality of antennae spacedan even multiple of a wave length apart and forming an antenna array,which consists in supplying froma remote central source energy for eachof said oscillators, tuning said antennae for substantial identity offrequency and simultaneously modulating the nected therewith and acommon modulating.

arrangements connectedwith said power circuit whereby the oscillationsof each oscillation circuit may be simultaneously varied, -9.- In a highfrequency signaling system, the combinationwith' a plurality of antennaespaced an evenmultiple of a wave length apart constituting an antennaarray, of a plurality of vacuum-tube oscillation circuits individual toand connected with each of said antennae and a power supply circuitcommon to all of said vacuum tube oscillation circuits to furnish theenergy necessary to create oscillations in said circuits.

10. In a high frequency signaling system, the combination with aplurality of antennae spaced an even multiple of a wave length apartconstituting an antenna array,

,tion circuits-to furnish the ener ling the waves oscillations of thedevice for modulating the of a plurality of vacuum tube oscillationcircuits individual to and connected with each of said antennae, a owersupply circuit common toall of said vacuum tube oscillanecessary tocreate oscillations in said circuits and modulating means connected withsaid power supply circuit for varying the oscilla tions set up in saidoscillation circuits.

11. In a directive radio system in which the antennae are spaced an evenmultiple of a wave length apart, the method of controlradiated from theplurality of antennae of such system, whichconsists in energizing from acentral point the'oscillation circuits individual to each antenna,tuning the oscillation circuits of each antenna to substantially thesame frequency and modulatin v from a central point the said oscillationcircuits in accordance with impressed signals. p

12. In a high frequencysignaling system, the combination with aplurality of antennae tuned to substantially the same frequency and sospaced as to have considerable interaction between them, of apluralityof vacuumtube oscilaltion generators indlvidual to andconnected witheach of said antennae, 'all of said oscillation generators beingadjusted to produce substantially the same frequency, avacuumtubemodulator,

a source of direct current connected with the plate electrodes of saidoscillationgenerators and said modulator, and a signaling high frequencyoscillations radiated by each of said antennae.

In testimony whereof, I have signed my name to this specification this11th day of November 1920.

RALPH BOWN.

